In conventional methods for defrosting a refrigerator using a heater, an inflow-preventing valve for preventing a refrigerant from flowing into an evaporator is closed in a state in which a compressor is operated, thereby forcibly reducing an amount of the refrigerant present inside the evaporator. There are methods that carry out the defrosting process based on heat produced by a defrosting heater in the above-mentioned state (for example, see JP-A-H10-38453).
FIG. 5 is a piping diagram of a cooling system, showing the conventional refrigerator-defrosting method disclosed in JP-A-H10-38453.
In FIG. 5, the cooling-cycle-system piping includes a compressor 101, a condenser 102, a dryer 103, a decompressor 104 (capillary tube), an evaporator 105, and a defrosting heater 106. An inflow-preventing valve 107 is provided between the condenser 102 and the dryer 103. The inflow-preventing valve 107 is closed in a state in which the compressor 101 is operated, thereby forcibly reducing an amount of a refrigerant present inside the evaporator 105. In that state, the defrosting process is carried out based on heat produced by the defrosting heater 106. This makes it possible to carry out the defrosting process while preventing the heat produced by the defrosting heater 106 from being consumed as vaporization heat of the refrigerant present inside the evaporator 105.